Insulating pressure-sensitive adhesive tapes for electrical parts, building materials including wall papers and sheets, and the like are frequently required to have flame retardancy. Such products which have been in general use are ones made of a poly(vinyl chloride) material. However, these products have a problem that they generate chlorine gas, which is corrosive, upon combustion to corrode external appliances. Furthermore, incineration disposal thereof also poses a problem, for example, that they generate chlorine gas and dioxins. Use of those products has hence come to be restricted.
Under these circumstances, the amount of magnesium hydroxide used as a flame retardant excellent in nontoxicity, less-smoking properties, and noncorrosive properties in flame-retardant resin compositions for use as materials for those products is increasing in recent years (see, for example, patent document 1).
However, in order for magnesium hydroxide to exhibit its flame retardancy, it is required to be added in a concentration as high as about 60% by mass based on the resin ingredient. Plastic composites into which magnesium hydroxide has been added in such a high concentration have a problem that they are reduced in mechanical properties and moldability (see, for example, patent document 2). This is attributable to the decrease in relative polymer amount resulting from the addition of such a large amount of magnesium hydroxide and to the hydrophilicity of magnesium hydroxide itself.
For overcoming those problems, it has been attempted to hydrophobized the surface of magnesium hydroxide with a higher fatty acid or to reduce the addition amount of magnesium hydroxide by mixing various auxiliaries (see, for example, patent document 3). However, even with these attempts, it has been impossible to obtain a fully satisfactory flame-retardant resin molding.    Patent Document 1: JP-A-2000-63583 (pages 1-2)    Patent Document 2: JP-A-2001-288313 (page 2)    Patent Document 3: JP-A-2002-128966 (pages 1-2)